Papers by Author: S.P. Lau

Abstract: Using a simple process of the deposition of ZnO thin films on SiOx/Si substrates and subsequent thermal annealing, we fabricated ZnO quantum dots embedded in silicon oxide matrix. The ZnO quantum dots were characterized using transmission electron microscopy and timeintegrated photoluminescence. The photoluminescence of the quantum dots show a blue-shift of 47 meV due to the quantum confinement effect.

Abstract: Nanocomposite Si containing amorphous carbon (a-C:Si) and metal containing amorphous carbon (a-C:Me) films including a-C:Al, a-C:Ti, and a-C:Ni were prepared by the filtered cathodic vacuum arc (FCVA) technique The metal-carbon (5 at.% metal) composite targets were used. The VCA Optima system was used to measure the contact angle. Three types of liquid were used to study the changes in the surface energy. X-ray photoelectron spectroscopy (XPS) was employed to analyze the composition and chemical state of the films. The surface morphology and roughness of the films were determined by atomic force microscopy (AFM). The Al containing films show the highest contact angle with water, which reaches as high as 101.26°. The Si containing films show the lowest contact angle around 64°. The contact angles of Ni, and Ti containing films are around 83°, 96.5°, respectively. The absorption of oxygen on the surface play an important role on the polar component of the a-C:Me films. The formation of Al-O, and Ti-O bonds is responsible for the lower polar component. The metal state Ni results in higher polar component. The Si-O bond contributes to the high polar component of a-C:Si film. As all films are atomic scale smooth, the RMS roughness is below 0.5 nm, the roughness does not have obvious effect on the surface energy.

Abstract: Zirconium oxide thin films were deposited at room temperature by using off-plane filtered cathodic vacuum arc (FCVA). Deposition rate, film structure, compositional analysis and optical properties are studied as a function of working pressure. Deposition rate as high as 53 nm/min could be achieved. As increasing working pressure, the film structure changes from Zr-O solid solution, to monoclinic structure with preferred orientation and finally to randomly oriented nanocrystalline structure. The averaged crystal size increases with working pressure and is less than 15 nm. The ratio of O/Zr increases with working pressure as well as transmittance and good stoichiometric film could be achieved with high transmittance of 91% at high working pressure.

Abstract: The intrinsic stress of tetrahedral amorphous carbon film as a function of annealing temperature is investigated. The film was deposited using the filtered cathodic vacuum arc technique and subsequently annealed at various temperatures. The stress is determined by Stoney’s equation using surface profilometry, and the microstructure is studied using atomic force microscopy, visible and ultraviolet Raman spectroscopy. It is found that as the annealing temperature increases the film stress decreases slowly up to 500 oC and then falls quickly at 600 oC. It is interesting to note that at this temperature sp3 fraction retains while sp2 clustering begins, which contributes to the sharp decrease in the stress.